Ca²⁺-Preintercalated V₂O₅ as a Dual-Function Cathode Additive for Polyiodide Anchoring in Zn-I₂ Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous zinc-iodine (Zn-I₂) batteries offer safe, eco-friendly, and resource-abundant energy storage.
• Performance limitations arise from active material shuttling and low Coulombic efficiency in conversion-type electrodes.

Purpose of the Study:

• To enhance the performance of Zn-I₂ batteries by addressing iodine shuttling and improving ion kinetics.
• To develop a high-performance cathode additive using calcium-ion-preintercalated vanadium pentoxide (CaVO) nanobelts.

Main Methods:

• Synthesized calcium-ion-preintercalated V₂O₅ (CaVO) nanobelts as a cathode additive.
• Fabricated composite cathodes (CaVO/AC@I₂) utilizing activated carbon and CaVO for iodine immobilization.
• Investigated synergistic effects of physical trapping and chemical adsorption for iodine and zinc-ion management.

Main Results:

• Achieved superior immobilization of iodine species and shortened Zn²⁺ diffusion pathways.
• Observed enhanced Zn²⁺ transport and capacity contribution due to Ca-induced crystal structure modification.
• Demonstrated high specific capacity (244 mAh g^-1 at 0.2 A g^-1), excellent rate capability (78.5% retention at 5 A g^-1), and energy density (279 Wh kg^-1).

Conclusions:

• The hybrid energy storage strategy using CaVO as a cathode additive significantly improves Zn-I₂ battery performance.
• Synergistic physical and chemical interactions effectively suppress iodine shuttling and facilitate ion transport.
• Presents a viable approach for developing next-generation high-performance aqueous batteries.